Autologous, fresh pulmonary emboli will be inserted into one main pulmonary artery of the dog, and the fate of the embolus studied at hourly intervals in control animals and in animals subjected to both hemorrhagic and traumatic shock. The lung will be studied grossly and microscopically and also will be analysed using the electronmicroscope. In addition, the fibrin split products will be studied in the pulmonary artery and pulmonary vein of the involved lung and the contralateral control lung. Utilizing the Todd technique, plasminogen activator in the lung will be assessed both on the emboli side and the control side to determine if there is an alteration of the fibrinolytic system. Subsequent to base line studies, a variety of therapeutic regimens including Destran,Heparinand Dipyrimadole will be assessed.